A stalker can be a fan, but a fan isn't necessarily a stalker. There is a line between an overtly interested fan and an annoying creep, though it probably isn't exactly the same among content creators. A fan may thoroughly enjoy the topic of the channel and feel connected to the channel creator because the two share the same passions. Internet etiquette being what it is, I'm sure a fan oversteps propriety now and again in his or her enthusiasm to connect with the person who makes the videos about things the fan really likes. A fan wants to know about the content maker, wants to see if there are other subjects of interest between them, wants to make a deeper connection than the typical viewer. Youtube is not really comparable to Hollywood, but if you think of a fan who is interested in a movie actor, the fan spends extra time reading about the actor and learning all sorts of things that help the fan feel connected to the actor.
Most people would consider a stalker to be someone who has crossed a line of some sort. Again, if you look at the Hollywood analogy, a stalker does things like follow the actor around town, intrude upon the actor's private moments with friends, send a continual stream of mail, and even enter the actor's private property. A stalker may not be dangerous, but his or her behavior disrupts the actor's life much more than a normal fan would. Do Youtube content creators have stalkers? Yes, they do, and they are similar to what Hollywood actors deal with. They intrude upon the personal lives of Youtube personalities and their attention-seeking amounts to harassment.
What is the line then between the two levels of fandom? First, it's a matter of intent. If a content creator feels a fan is crossing the line, he or she should say something to get an idea whether the fan has more on the mind than simply trying to relate with the maker of the videos more deeply. I'm flattered when people who watch my videos send me messages and want to know things about me. Not everyone feels this way, so those people may need to express where their particular fan line is and understand that exuberance isn't necessarily stalking. Give your fans a break and say what you're comfortable with and what you're not.
I'm a fan myself of several Youtube content creators, but I don't think I've ever crossed the line into stalkerhood despite my special interest in certain video producers who intrigue me with their skill, knowledge, and personalities. So give your viewers a break, give your fans a break, because a fan may just be a socially clumsy individual who likes the stuff you do so much that he or she wants to relate on a deeper level. A stalker wants to steal your used napkins; a fan just wants you to acknowledge their admiration.
That is all. Return to work everyone!